THE NE.,W YORKER norma] response patterns. For example, Warren Roberts discovered a focal point in the cat's brain where stimula- tion had a paradoxical effect: first re- warding and then aversive. (A trained anImal would press a lever to tu rn on such stimulation, press another lever to turn it off, and then alternate between the two levers indefinitely.) This was a curious phenomenon no matter how you looked at it-but its significance depended somewhat on whether a single neural mechanism was involved, or two separate but re- lated mechanisms., or two functionally independent mechanisms that just hap- pened to lie near each other at this point in the brain. To get a better idea of what was actually going on in the electrically .,timulated focal puints in the brain, Mil]er and his associates turned to an even newer, and potentially more so- phisticated research tool: chemical stim- ulation of the brain. By seedIng a target area with small amounts of substances that normally occur in the synapses be- tween nerve cells, the researchers were able to show that the neural control of behavior is, in a literal sense, chem- ically coded. When one of Miller's students, Sebastian P. Grossman, ap- plied tiny crystals of acetylcholine to a certain area of the hypothalamus, a rat that had just eaten and drunk to satia- tion started drinking again, but when crystals of norepinephrine were applied to precisely the same area, the satiated rat began to eat instead. Even strang- er contrasts appeared when a single substance was applied to different tar- gets a few millimetres apart. A re- searcher in another lab found that a very small amount of male horl11one injected into the rat's hypothal- '. amus could elicit typical male .f ' sexual responses or typical ma- ternal behavior in animals of either sex, depending on the site of the injection. The results of these brain probes were so fascinating in them- selves and so suggestive of exciting breakthroughs that for a while in the nineteen-fifties MIller found it dif- ficult to interest himself or his gradu- ate students in any other work. But gathering experimental data is one thing, and fitting them into a mean- ingful pattern is another. It was clear that the brain was the last frontIer of both physiology and psychology-the ultimate test of n1an's ability to under- stand himself. The use of electrical and chemical stimulation had so far pro- vided a few tantalizing glimpses of the brain's operation-just enough to make men realize how crude even their most II · .- . ."" -- ad vanced theoretIca] models were The drive-reduction hypothesis was a prime example; some experiments seemed to suppurt it, others to contradict it. The conclusive test that Miller had hoped for would have to wait until more was known about the brain mechanisms themselves-and in the meantime there was a good chance that someone would devise a broader, more useful hypothesis to make sense out of the mass of new materIal emerging from the laboratories. While keeping an eye on all these devel- opments, in his own lab and elsewhere, Miller was eager to apply what had al- ready been learned to a closely related, and long neglected, problem: the instru- mental conditioning of visceral responses. I N 1957, Miller had come across an English translation of a book bv K. M. Bykov, a RussIan physiologist who headed a laboratory in Leningrad devoted to behavorial research in the Pavlovian manner. Bykov's book (orig- inally published in the Soviet Union in 1941) gaVe a detdiled accOunt of the creation of conditioned reflexes involv- ing all kinds of internal functiuns. Mil- ler was especially impressed by evidence that such deeply buried visceral re- sponses as the formation of urine in the kidneys, contractions of the uterus, and the ejection of red blood cells from the spleen could be classically conditioned to a neutral stimulus (just as a dog could be conditioned to salivate at the ringing of a bell). Bykuv's success in bringing a wide range of visceral re- sponses under such precise stimulus cun- trol prompted Miller to reëxamine his own research priorities. Since he was committed to the view that th ere is a fundamental unity to all learning, he had to assume that whatever 4 Þ Byko\ and his co-workers had accomplished uSIng the tech- niques of classical conditioning could be duplicated by a re- searcher using the techniques c,t of instrumental learning. In fact, looking back on his early days at the [nstitute of Human Relations, he found it remarkable that none of Hull's students had made a serious effort to investigdte the possibility of visceral learning. "With so many oth- er people insisting that it couldn't he done, even the smallest positive re- sult would have been a terrific coup for our theory," Miller commented recen tly. As for himself, he could only conclude, "I may have dodged this particular application of Hull's theory because I felt that it might be refuted here, and I was uncon- sCIously reluctant tu face this possible outcome-either out of loyalty to Hull II .- . 47 I Jumping around ':,: : ::: :. ::. . -:: :::;:::, ", "v; $. .. " , : '", ", t ..:: A .' : .'" ,'r ::1: " " '. .... >. * '-: 4 1+. -{. . ... :-:...:" ......-. : '-< t:t. 0 '",. "",., '. ,. . M"'<,'" . ." , , 'H"" . ( .... : ..' + 'l-.i : Wf .'f:' h . ? ;.; ,,"2F> > d '> "(t ^ 'w . . ,X'- """ . \ þ, , , >' . .. :;: '.:. 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